1. Technical Field
The present invention relates to a piezoelectric device and an electronic apparatus, and more particularly relates to a piezoelectric device that has a piezoelectric resonator element and a circuit which oscillates the piezoelectric resonator element, and to an electronic apparatus having such piezoelectric device.
2. Related Art
There is a piezoelectric device having a piezoelectric resonator element and a circuit (an oscillation circuit) that is conductively coupled with the piezoelectric resonator element and oscillates the element in a package. JP-A-2004-15441 is a first example of related art. The oscillation circuit is an integrated circuit (IC) chip having an active face where a pad to which a wire is coupled is provided. According to the first example, the package includes a package base that has a concave portion whose opening faces upward and a lid that is placed onto an upper face of the package base and seals the concave portion. The concave portion has a lateral face which is formed in a stair-like shape and two step portions are provided there. The IC chip whose active face is directed upward is fixed onto a bottom face of the concave portion. A wire couples the pad that is provided on the active face with a pad electrode that is disposed on a lower step portion. The piezoelectric resonator element is bonded and fixed onto a package-side mount electrode (mount electrode) which is provided on an upper step portion by using a conductive adhesive. As described above, in the piezoelectric device, the IC chip and the piezoelectric resonator element are arranged in a vertical direction such that a principal plane of the piezoelectric resonator element faces the active face of the IC chip and the wire is provided between the principal plane and the active face.
JP-A-2006-20140 is a second example of related art. The second example discloses a piezoelectric oscillator in which a piezoelectric resonator element and an IC chip are disposed in a vertical direction, and a longer side of the IC chip and a longer side of the piezoelectric resonator element cross each other when they are viewed in plan. In this case, a shorter side of the IC chip does not cross over the piezoelectric resonator element when viewed in plan therefore it is possible to dispose a pad in an area where the IC chip and the piezoelectric resonator element do not overlap each other. In this way, a wire is not arranged between the principal plane of the piezoelectric resonator element and the active face of the IC chip.
In case of the piezoelectric device in which a wire is disposed between the principal plane of the piezoelectric resonator element and the active face of the IC chip as described in the first example, a gap for avoiding the piezoelectric resonator element from contacting with the wire should be provided because an oscillation defect and the like can occur when the piezoelectric resonator element and the wire contact each other. However, when the gap between the piezoelectric resonator element and the wire is wide, it is impossible to make the piezoelectric device thin.
In case of the piezoelectric device in which the longer side of the piezoelectric resonator element is arranged so as to cross over the longer side of the IC chip when viewed in plan and the pad is disposed laterally to the piezoelectric resonator element as described in the second example, there is a disadvantage of a large planar size of the piezoelectric device. Moreover, the IC chip has to be made in a rectangular shape when viewed in plan and the pad should be disposed along the shorter side of the IC chip. This particular arrangement of the pad limits the versatility of the IC chip use such that it cannot be used for some different arrangements in the package even with a piezoelectric device having the same function.